[Immunochemical identification of beta1-globulin of the "pregnancy zone" in serum of patients with trophoblastic tumors]

Molecular cloning of a cDNA for human pregnancy-specific beta 1-glycoprotein:homology with human carcinoembryonic antigen and related proteins

Human pregnancy-specific beta 1-glycoprotein (SP1) plays an essential role in normal pregnancy. It is also a well-characterized oncodevelopmental antigen, expressed aberrantly by all trophoblastic tumors and some other malignant cell types. Here we report the identification of a human placental cDNA encoding the SP1 polypeptide sequence. The coding sequence shows 95% identity at the nucleotide level with a distinct, recently published SP1 cDNA sequence (PSG16). Unexpectedly, the sequence is also highly homologous to the published sequence of human carcinoembryonic antigen (CEA). SP1, CEA and CEA-related nonspecific cross-reacting species thus belong to a group of closely related though antigenically diverse tumor-associated glycoproteins. Comparison of the deduced amino acid sequence of the SP1 cDNA with that of CEA provides insight into the modular nature of these related proteins. This may have implications for the genomic organization and evolution of the CEA gene family.

Serum levels of six tumor markers in patients with benign and malignant gynecological disease

We studied the pretreatment serum levels of 6 tumor markers in gynecological patients with and without malignant disease. The tumor markers were carcinoembryonic antigen (CEA), tissue polypeptide antigen (TPA), ferritin, Schwangerschaftsprotein 1 (SP1), Schwangerschaftsprotein 3 (SP3) and cancer antigen 125 (CA125). The results were as follows: (1) Serum CA125 and TPA levels were raised in 81% and 57% of patients with ovarian serous cystadenocarcinoma; CEA and SP3, in 52% and 43% respectively of patients with ovarian mucinous cystadenocarcinoma; CA125, TPA and SP3, in 76%, 48% and 48% respectively of patients with other ovarian malignancies; and TPA and SP3, in 56% and 40% respectively of patients with endometrial carcinoma. (2) Serum levels of TPA, ferritin and CA125 were more often raised with advancing stages of malignant disease. (3) Serum TPA levels were elevated in 55% of patients with stage I endometrial carcinoma, and serum SP3 levels were elevated in 35% of patients with a stage I malignant ovarian neoplasm and in 45% of patients with endometrial carcinoma. (4) One of the 6 tumor markers showed a raised level in 84% of patients with gynecologic malignancy as against 56% in those with benign gynecologic diseases.

Gestational trophoblastic diseases: the ratio of choriogonadotropin to specific pregnancy protein, hCG/SP1, provides useful diagnostic and prognostic evidence

Serum levels of human chorionic gonadotropin (hCG), specific pregnancy protein (SP1), and hPL were measured in 675 samples from women with uneventful pregnancy, and serially from the time of presentation in 125 patients with hydatidiform mole (HM), 43 with invasive mole (IM), and 34 with choriocarcinoma (CC). In HM serum levels of hCG and SP1 declined steadily from presentation to remission; when gestational age at the time of molar evacuation was shorter than 11 weeks, hCG declined to the normal range later than SP1 (57% patients), and when the age was longer--at the same rate as SP1 (26% patients) or earlier (17% patients). Serum levels of either marker were higher in IM than in HM and tended to increase, and in CC were either lower or higher than in IM. Treatment was followed by parallel decline of either marker, although SP1 declined to the normal range later than hCG in 12% of patients with IM and in 10% with CC. The hCG/SP1 ratios in normal pregnancy declined exponentially between the beginning and 23rd week of gestation and stayed level thereafter. The ratios calculated for the gestational age at the time of initial evacuation of the uterus or delivery were close to those of normal pregnancy in 80%, slightly increased in 20% of patients with spontaneously regressing HM, and markedly increased in 70% of patients with IM and in 74% of patients with CC. The ratios tended to increase during chemotherapy. An increase in the hCG/SP1 ratio seemed to be a characteristic sign of malignant change when compared with this ratio in normal pregnancy and hydatidiform mole. Determination of SP1 for monitoring therapy seemed redundant, and hPL assay was useful for discrimination between relapse and pregnancy.

Prognostic value of concentration of pregnancy-specific beta 1-glycoprotein (SP1) in serum of patients with breast cancer

Pregnancy-specific beta 1-glycoprotein (SP1) was assayed by particle counting immunoassay in serum from 46 healthy female blood donors, 33 patients with benign mastopathy and 84 patients with breast cancer before operation and during follow-up. Values greater than 1 micrograms/1 were found more frequently with benign mastopathies (11/33) and in patients with breast cancer at stage 2 (20/48), 3 (4/9), and 4 (7/10) than in healthy female blood donors (3/46). The survival rate after 4 years was significantly lower in patients with SP1 level greater than 1 microgram/1 before tumor resection (52% vs. 87%). The difference remained significant when only patients in stage 2 were taken into account (57% vs. 85%). A highly significant (r = 0.64; N = 46) negative correlation was observed between the concentration of SP1 in serum and the concentration of estrogen receptor in the tumor. The longitudinal study of patients in stage 2 indicated that, of the 15 whose SP1 concentration fell below 1 microgram/1 after operation, 14 survived over 4 years whereas during the same period, 9 of the 10 patients whose SP1 value remained higher than 1 microgram/1 died.

Gestational trophoblastic tumors

Although virtually 100% of women who develop gestational trophoblastic tumors enter a long-term complete remission, there are many aspects of trophoblastic disease that arouse interest. Epidemiological studies have shown a large geographical variation in the percentage of conceptions that result in a hydatidiform mole and have stimulated studies on the immunological differences of the low and high risk populations. Chromosomal analysis is now complementing the pathological differentiation between complete and partial moles. There is still debate as to which factors are positively associated with the progression of a hydatidiform mole through invasive mole to choriocarcinoma. There are also considerable differences in the proportion of molar patients receiving chemotherapy in different centers. In addition to these topics, this article will review several recently introduced treatment regimens which show improved results with reduced toxicity.

Is SP-1 a marker for testicular cancer?

We measured the serum levels of the pregnancy-associated protein SP-1 by radioimmunoassay in 91 patients with a diagnosis of germ cell testicular cancer. Sixty-seven of the men had active disease, and of these, 52 per cent had elevated levels of SP-1. In contrast, all 24 patients with inactive disease had normal levels. Elevations of SP-1 were associated more often with elevated levels of human chorionic gonadotropin than with elevated levels of alpha-fetoprotein, but elevated SP-1 levels also occurred in patients with normal levels of both of these established tumor markers. We studied serial samples from 21 patients, and in 5 the SP-1 level provided clinically valuable information not provided by the other two markers. SP-1 is a clinically useful marker in germ cell testicular cancer. Further studies are needed to determine the role of the two forms of protein, alpha and beta, and to define the conditions under which the SP-1 level is elevated.

Is SP1 (pregnancy specific beta 1 glycoprotein) elevated in cancer patients?

Pregnancy-specific beta 1-glycoprotein, SP1, was measured in serum by competitive double antibody radioimmunoassay. Very low levels of SP1 or SP1-like activity were found in only 2 out of 85 sera from patients with cancer of the digestive tract, breast cancer, melanoma, and sarcoma, in 2 out of 11 sera from patients with infectious diseases, and in none out of 15 sera from non-pregnant healthy individuals. SP1 thus does not seem to be ectopically produced in vivo by the types of cancer studied, but is probably highly specific for the normal and malignant trophoblast.

Human fibroblasts produce "pregnancy-specific" beta-1 glycoprotein in vitro

Normal and genetic variant strains of nonmalignant human fibroblasts produce in vitro a substance indistinguishable from the recently described "pregnancy-specific" beta-1 glycoprotein (PSbetaG, PAPP-C, SP1). Demonstration of this presumed placenta-specific material in a nonplacental site raises questions about its normal physiologic role and use as a cancer marker.

The quantitation of pregnancy specific beta 1-glycoprotein by enzyme linked immunoassay

A rapid enzyme linked immunoassay for pregnancy specific beta 1-glycoprotein is described. The method is sensitive and precise (within batch C.V. = 6.5-7.4%) and should be suitable for the biochemical monitoring of pregnancy and the investigation of patients suffering from various malignancies.

Human embryonic prealbumin as a marker for tumours and fibroblasts

Embryonic prealbumin (E.P.A.) was demonstrated by agar immunodiffusion in 122 out of 505 homogenates of various tumours and in 7 out of 20 serum samples from patients with connective-tissue tumours. Analogous antigen was found in human embryonic and adult cultured fibroblasts. This newly identified antigen is probably actively secreted by fibroblasts into the circulation of patients with tumours.

Development of radioimmunoassay for pregnancy-specific beta1-globulin and its measurement in serum of patients with trophoblastic and non-trophoblastic tumours

Levels of human pregnancy-specific or trophoblast-specific beta1-globulin (TBG) were measured by double-antibody radioimmunoassay (RIA) in 103 patients with trophoblastic tumours and in 114 patients with a variety of non-trophoblastic tumours. The sensitivity of RIA for TBG was about 1 ng per ml. Twenty healthy adult females and males had levels below 1 ng per ml. Using the RIA for measurement of TBG in sera which were selected from immunodiffusion-TBG-negative samples, we detected elevated TBG levels in 76.7% of cases with trophoblastic tumours and in 15% of different cases with non-trophoblastic malignancies. The diagnostic and prognostic significance of the measurement of TBG levels by RIA in patients with trophoblastic tumours is discussed.

[Antifertility effect of an active immunization of monkeys with human pregnancy-specific beta 1-glycoprotein (SP1) (author's transl)]

Fertile female cynomolgus monkeys (Macaca fascicularis) were actively immunized against human pregnancy-specific beta 1-glycoprotein (SP1). Native SP1 as well as chemically modified derivatives of SP1 served as antigens. The effect of the immunization on reproduction in these animals was investigated. The immunized monkeys showed a significant reduction in fertility: the conception rate in these animals was only slightly reduced when compared with the controls; but in the immunized monkeys pregnancy often resulted in abortion. The possibility of using immunization against SP1 as a contraceptive method in man is discussed.

Human pregnancy-specific beta1-globulin and its relation to chorioepithelioma

Human serum pregnancy-specific beta1-globulin (beta1-GP) was localized in paraffin sections of placenta and chorioepithelioma of the uterus by indirect immunofluorescence. The structures containing beta1-GP but not human serum albumin were regarded as specifically associated with beta1-GP metabolism. Beta1-GP was found in trophoblastic cells of chorion and Langhans cells of chorioepithelioma. Using the immunoautoradiographic method (I131), we only found beta1-GP in sera of patients with trophoblastic tumours: in 74.3% of 35 patients with chorioepithelioma and in 80% of 25 patients with hydatidiform mole and destructive hydatidform mole. The diagnostic and prognostic significance of the immunochemical test for beta1-GP in trophoblastic tumours is discussed.